Nanometer scale-electrochromic modification of NiO films using a novel technique of scanning near-field optical microscopy

Nanometer-scale observation and modification of NiO films were performed using a novel technique for scanning near-field optical microscopy (SNOM) combined with a current-sensing function. The novel SNOM was newly developed in order to investigate not only local optical distributions but also local electrical properties of EC materials. In order to detect optical and electrical properties at a local point on the material surface, a cantilever-type metal probe was fabricated. The near-field optical properties could be observed using the local field enhancement effect generated at the edge of the metal probe under p-polarized laser illumination. In regard to electrical observation, the current signal could be observed using the metal probe connected to a highly sensitive current amplifier. The surface topography, optical distribution and current image of the colored electrochromic (EC) material of NiO films were observed simultaneously using the current-sensing SNOM. Furthermore, nanometer-scale EC modification of local bleaching could be performed using the current-sensing SNOM. The current-sensing SNOM opens up new fields of EC materials in nanometer-scale optelectronic applications.